The invention pertains to interbody vertebral stabilization. Specifically, the invention is directed to devices and procedures for stabilization of vertebral bodies using external and intervertebral stabilizing systems. The invention is particularly advantageous for stabilizing lumbar vertebrae.
Chronic back problems cause pain and disability for a large segment of the population. In many cases, the chronic back problems are caused by intervertebral disc disease and loss of stability of the intervertebral joint. Stabilization and/or arthrodesis of the intervertebral joint can reduce the pain and debilitating affects associated with disc disease.
Spinal stabilization systems and procedures have been developed to stabilize diseased intervertebral joints and, in some cases, to fuse the vertebrae that are adjacent to the diseased joint space. Most fusion techniques include removing some or all of the diseased disc material from the affected joint, stabilizing the joint and inserting a bone graft or other material to facilitate bony fusion of the vertebrae.
One type of spinal stabilization system includes screws and connecting rods which can be used for stabilizing many spinal conditions including, for example, degenerative disc disease, scoliosis, spondylolithisis and spinal stenosis. Examples of such systems are disclosed in U.S. Pat. Nos. 6,010,503; 5,946,760; 5,863,293; 4,653,481, etc., the entire disclosures of which are incorporated herein by reference. In these systems, a bone screw (e.g., pedicle screw) is typically anchored into each vertebral body to be stabilized and a rigid connecting rod mounted to the screws to fix the vertebrae in a particular relative position. Generally, these systems provide posterior column support but lack anterior column support.
Another type of spinal stabilization system includes interbody implants such as disclosed in, for example, U.S. Pat. Nos. 5,458,638; 5,489,307; 5,055,104; 5,026,373; 5,015,247; 4,961,740; 4,877,020; 4,743,256; and 4,501,269, the entire disclosures of which are incorporated herein by reference. Some of these implants are bone, some are solid titanium or similar non-bone implant material and some are hollow implants that provide for inclusion of a bone graft or other suitable material to facilitate bony union of the vertebrae
Interbody implants can be inserted into the disc space through an anterior, posterior or lateral approach. When two implants are used, the implants are typically positioned parallel to one another on either side of a sagittal plane passing through the midline of the vertebral bodies. In some systems, the implants are inserted into a bore formed between adjacent vertebral bodies in the cortical endplates and can extend into the cancellous bone deep to the cortical endplates. Implant size is typically selected such that the implants force the vertebrae apart to cause tensing of the vertebral annulus and other soft tissue structures surrounding the joint space. Tensing the soft tissues surrounding the joint space results in the vertebrae exerting compressive forces on the implant to maintain the implant in place.
However, in some cases, the compressive forces exerted on the implant may cause undesired pressure induced changes to the bone adjacent the implant. Pressure induced changes can lead to reduced joint stability, increased fusion time and increased chance of subsidence or implant migration.
Accordingly, there is a continuing need for improved vertebral stabilizing devices and methods. The present invention is directed to addressing these needs.
The present invention is directed to instruments and methods for stabilization of vertebral bodies adjacent an intervertebral disc space using bilateral external stabilization systems and intervertebral implants.
In one embodiment, the invention provides a method for stabilizing an intervertebral joint between adjacent first and second vertebral bodies from a posterior approach. The method includes a step of forming an implant bore between the adjacent vertebrae for receiving an intervertebral implant. An intervertebral implant is then inserted into the implant bore. A bilateral external stabilization arrangement, such as known pedicle screw and rod fixation systems can be mounted to the adjacent vertebrae before or after preparing the implant bore and inserting the intervertebral implant.
In another embodiment, the invention provides a surgical procedure for stabilizing an intervertebral joint between adjacent first and second vertebral bodies using an interbody implant inserted into the intervertebral disc space with the longitudinal axis of the implant oriented at an angle oblique to a sagittal plane passing through the midline of the vertebral bodies. Bilateral external stabilization systems can be applied before or after insertion of the intervertebral implant.
The invention also provides new instruments including an instrument guide for guiding instruments for preparing an implant site and inserting the implant into the implant site. The instrument guides include a distal edge having an oblique angle that can rest on the exterior surface of the vertebrae such that the longitudinal axis of the guide can be at an angle oblique to a sagittal plane passing through the midline of the vertebral bodies. The instrument guides of the invention can also include distally extending paddles to stabilize the instrument guide during use and to distract and/or maintain distraction of the intervertebral disc space to a predetermined height during an implant procedure.
Kits will also be available including instrument guides of the invention having various sized lumens and paddle widths for corresponding to different implant diameters and disc space heights. The kits can also include boring instruments, taps, depth gauges, etc., which may be necessary to perform a procedure according to the invention.